There is a growing awareness of the importance of diet, and there is a consciousness among many people that certain ingredients may be harmful to their health. Persons who are allergic to certain ingredients may suffer adverse reactions, including in extreme cases anaphylactic shock and death, as a result of ingesting such ingredients.
Others have been advised by their doctors to avoid such things as cholesterol or sodium. Some people simply dislike the taste of certain ingredients.
Typically, a restaurant menu provides little information to the customer about what ingredients are in the recipe of any given serving listed on the menu.
An allergic person may have to engage in a long discourse with the waiter regarding an ingredient the allergic person is trying to avoid, with the waiter making frequent trips to the kitchen to consult with the cook about his recipes.